The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Thermal spraying is a coating process which applies material heated and typically melted by combustion or an electrical plasma or arc to a substrate. The process is capable of rapidly applying a relatively thick coating over a large area relative to other coating processes such as electroplating, sputtering and physical and vapor deposition.
The ruggedness and durability of the thermal spray coating would seem to be almost exclusively a feature of the material of the coating and to a lesser extent the quality of application. However, it has been determined that, in fact, typically the most significant factor affecting the ruggedness and durability of a thermal spray coating is the strength of the bond between the thermal spray coating and the substrate. A poor bond may allow the thermal spray coating to slough off, sometimes in relatively large pieces, long before the thermal sprayed material has actually worn away whereas a strong bond renders the thermal spray coating an integral and inseparable component of the substrate.
Several approaches have been undertaken to improve the bond between the thermal spray coating and the substrate. Typically these involve adjusting the composition of the thermally sprayed material and adjusting process parameters such as substrate temperature, application energy (and thus application velocity and temperature) and ambient conditions. The present invention is directed to another approach to improving the adhesion of thermal spray coatings to a substrate.